Arc rupturing device for electric safety fuses



E. LANGE Feb. 5 1, 1939.

ARC RUPTURING DEVICE FRELGTRIC SAFETY FUSES Filed March 23, 193'?Patented Feb. 21, 1939 ARC RUPTURING DEVICE FOR ELECTRIC SAFETY FUSES IEmil Lange, Berlin-Zehlendorf, Germany Application March 23, 1937,Serial No. 132,583 In Germany March 27, 1936 3 Claims.

This invention relates to a safety fuse for high tension electriccurrents and of the kind wherein fuse wires which connect the terminalsof an enclosing casing are adapted, on fusing, to form 5 one arc at anarrow outlet in the casing and another arc in a space the fluidcontents*y of which, on being heated by the arc, causes the fluidoutside the space to be ejected through the outlet for rupturing thearc.

Fuses of this kind have the property of taking up the full strength ofthe short-circuit current, and it is therefore necessary to make thestructure of dimensions capable of coping with the largest currents thatcan be expected.

The object of the present invention is to obtain a construction whichallows the fuse to be of comparatively small dimensions, and theinvention consists essentially in providing the casing with a resistorhaving one terminal perma- 29 nently connected to the fuse circuit andanother terminal arranged so as to attract and make contact with one ofthe arcs on the fusing of thc wires, thereby reducing the current owingthrough the arcs.

Fig. l of the accompanying drawing represents a sectional View of ,afuse constructed according to the invention, and

Fig. 2 is a sectional view a modified form.

Referring first to Fig. 1 it will be seenv that the fuse structurecomprises an insulating casing which is closed at one end by a cap |08forming one terminal of the fuse. The other end of the casing is fittedwith an insulating member 2 having a central, narrow opening forming anoutlet :i5 for thc uid in the casing. The outlet also forms a seatingfor a spring pressed valve whereby said outlet is normally closed. Anannular metallic member |09 surrounding the outlet forms 'the secondterminal of the fuse. Supported centrally within the casing is a tubularinsulating member 3 one end of which faces the outlet and is closed byan insulating member |05. A metal conductor |05, fitted in theinsulating member |06, forms a contact member between two fuse wires |04and |03, The wire |04 is attached to the terminal |09, and the Wire |03is attached to the terminal cap |08.

On the fusing of the wires one arc will be o formed between theconnecting member |05 and the terminal |09, and another arc will beformed inside the member 3. The fluid contained in 'the space |02 of thelatter will be expanded by the heat and cause the colder fluid in theoutside space |0| to be ejected through the narrow outlet, therebycausing an effective rupturing of the arc formed at the outlet.

According to the invention a tubular resistor is arranged within themember 3 with one end in contact with the connecting member |05 5through the medium of washers` ||3 of copper or other good conductingmaterial. The opposite vend of the resistor is fitted with a similarwasher |2, and the central space I4, through which the Wire |03passesgis fitted with a lining ||5 of 10 asbestos or other insulatingmaterial, the resistor being thus enclosed in insulation except for thefree end thereof to which the copper washer 2 is connected. Thus, whenthe wire fuses, the arc will bc attracted by and connect with theresistor through the metal washer ||2, and the current flowing throughthe arc at the outlet will therefore be reduced in strength.Consequently the pressure curve, which follows the rising strength ofthe current, will not attain the value of the entire short-circuitcurrent.

Fig. 2 shows a construction in which the resistor |2| is arranged so asto form the outlet of the fuse casing 4. A central tubular member 5,supported as previously described, carries in a closing member 6 ofinsulating material a conductor ||8 which forms a connecting memberbetween the fuse wires and ||9. The latter passes through a lateral ductin the resistor |2| for connection to an annular terminal |20 mounted soas to be exposed at the side of the casing 4. A cap l, which surmountsthe casing 4, is provided with gas outlets |23 and guides a springcontrolled valve |22 which normally closes the outlet of the resistor|2|. 35

On the fusing of the wires, the arc formed at the outlet of the casingwill be attracted by and connect with the resistor forming said outlet,and the current will be correspondingly reduced.

By a proper dimensioning of the resistor, the 40 current allowed to passthrough can be determined, and excessive Values of such current can thusbe ebviated. I'his allows a reduction in the size of the fuse structureand also prevents the rupturing of the arc from being retarded by a toostrong current.

I claim:

1. An electric safetv fuse of the character described comprising aninsulating casing containing a fluid and having at one end thereof anarrow outlet for said fluid, a contact member at each end of thecasing, a confined space in said casng communicating with the outletthrough a circuitous route, fuse Wires connecting the contacts throughthe outlet and through said space so that, on a fusing of the Wires,arcs will be formed at the outlet as well as in said space, and so thatthe heating of the fluid in the latter will cause the fluid outside thespace to be ejected through the outlet for rupturing the arc, and aresistor having one terminal permanently connected to the fuse circuitand another terminal arranged in position to attract and connect withone of the arcs for reducing the strength of the current.

2. An electric safety fuse of the character described comprising aninsulating casing containing a uid and having at one end thereof anarrow outlet for said fluid, a contact member at each end of thecasing, a conned space in said casing communicating with the outletthrough a circuitous route, a. pair of fuse wires arranged in series andconnecting the contacts through the outlet and through said space sothat, on a fusing of the wires, arcs will be formed at the outlet aswell as in said space and so that the heating of the uid in the latterwill cause the uid outside the space to be ejected through the outletfor ElVIIL LANGE.

